fix: bump react toolkit cma dependency to v12

[Jared Jolton (jjolton-contentful)]

Fixes #3081

Summary

• Bump @contentful/react-apps-toolkit from contentful-management v11 to the v12-compatible ^12.3.1 range.
• Require @contentful/app-sdk >=4.54.0, which is the app-sdk line that also depends on contentful-management v12.
• Update the lockfile so the toolkit and app-sdk compile against the same CMA v12 type surface.

Breaking change

• @contentful/react-apps-toolkit now requires @contentful/app-sdk >=4.54.0.
• contentful-management v12 declares node >=20.

Upgrade instructions

• Upgrade @contentful/app-sdk to 4.54.0 or later before upgrading @contentful/react-apps-toolkit to the version released by this PR.
• Run the app on Node.js 20 or later to satisfy the contentful-management v12 engine requirement.
• If the app imports contentful-management directly, align that dependency to v12 as well to avoid bundling multiple CMA major versions.

Release notes

• No checked-in changelog entry is added manually. This repository uses Nx release with projectChangelogs and Conventional Commits, so the release workflow will generate the package changelog and GitHub release notes from the BREAKING CHANGE commit footer after merge.

Test plan

• node -e "const pkg=require('./packages/contentful--react-apps-toolkit/package.json'); if (!/^\\^12\\./.test(pkg.dependencies['contentful-management'])) { throw new Error('react-apps-toolkit must depend on contentful-management ^12.x'); } for (const field of ['peerDependencies','devDependencies']) { if (pkg[field]['@contentful/app-sdk'] !== '>=4.54.0') { throw new Error(field + ' @contentful/app-sdk must require >=4.54.0 for contentful-management v12 compatibility'); } } console.log('metadata ok');"
• npm ls @contentful/app-sdk contentful-management --workspace @contentful/react-apps-toolkit --depth=1
• npm test --workspace @contentful/react-apps-toolkit -- --runInBand
• npm run build --workspace @contentful/react-apps-toolkit
• git diff --check

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